Light emitting element and manufacturing method thereof

ABSTRACT

In order to provide a light emitting device which consistently emits light at the time of continuous driving in addition to obtain light emission having a high color purity in each of red, green and blue, a light emitting element according to the present invention, in which an organic compound film comprising a hole transporting material, an electron transporting material, a first impurity (first doping material), and a second impurity (second doping material) is provided between an anode and a cathode, is characterized in that the organic compound film is laminated with a first mixed region comprising the hole transporting material and the first impurity, a hole transporting region comprising the hole transporting material, a second mixed region comprising the electron transporting material and the second impurity, and an electron transporting region comprising the electron transporting material in order from the side of the anode.

This application is a divisional application of application Ser. No.10/766,170 filed on Jan. 27, 2004 now U.S. Pat. No. 7,053,402.

TECHNICAL FIELD

The present invention relates to an organic light emitting elementcomprising an anode, a cathode and a film comprising an organic compound(hereinafter, referred to also as “organic compound film”) which canobtain light emission by being applied with an electric field and amethod for manufacturing the light emitting element.

BACKGROUND OF THE INVENTION

An organic light emitting element is an element which emits light bybeing applied with an electric field. A light emitting mechanism is saidto be that an organic compound film is interposed between electrodes,voltage is applied to them, an electron injected from a cathode and ahole injected from an anode are recombined in the organic compound filmto form a molecule in an excited state (hereinafter, referred to also as“molecular exciton”), and then, light is emitted by allowing energy tobe discharged when the molecular exciton returns to a base state.

As for the type of the molecular exciton which is formed by the organiccompound, those in a singlet excitation state and a triplet excitationstate are considered to be possible. Herein, a case in which any one ofthem contributes to light emission is included.

In such organic light emitting element as described above, ordinarily,the organic compound film is formed with a thickness as low as less than1 μm. Further, since the organic light emitting element is an element ofa self-light emitting type in which the organic compound film itselfemits light, the organic light emitting element does not require abacklight which has been used in an ordinary liquid crystal display.Therefore, there is a large advantage in that the organic light emittingelement can be manufactured to be extremely thin and light-weight.

Further, for example, in the organic compound film of approximately from100 to 200 nm, a period between the time a carrier is injected and thetime it is recombined is only several tens of nanoseconds when atransportation rate of a carrier is taken into consideration so thatlight is emitted in the order of microseconds even including a processof from such recombination of the carrier to light emission. Therefore,an extremely fast response speed is also one of characteristics.

Further, since the organic light emitting element is a light emittingelement of a carrier injection type, it is capable of being driven by adirect current voltage and hardly generates noises. As for the drivingvoltage, firstly thickness of the organic compound film is allowed to beof an ultra thin uniform film of about 100 nm, and then, an electrodematerial in which a carrier injection barrier is allowed to be smallagainst the organic compound film is selected and, further, aheterostructure (double layer structure) is introduced and, as a result,such sufficient brightness as 100 cd/m² is attained at 5.5 V (forexample, refer to Non-Patent Document 1).

(Non-Patent Document 1): C. W. Tang et al., Applied Physics, Letters,1987, Vol. 51, No. 12, pp. 913 to 915.

From these characteristics, namely, thin light-weight, a rapid responseproperty, direct current low voltage driving and the like, the organiclight emitting element has been paid attention as a flat panel displayelement of a next generation. Further, since it is a self-light emittingtype and has a wide viewing angle, it is comparatively favorable invisibility and is considered effective as an element for use in adisplay panel for portable appliances.

Incidentally, as for a structure of the organic light emitting elementas shown in Document 1, as a method for allowing the carrier injectionbarrier to be small against the organic compound film, an Mg:Ag alloywhich is not only low in work function but also stable is used as acathode, to thereby enhance an electron injection property. For thisaccount, it has become possible to inject a large amount of carriersinto the organic compound film.

Further, as for the organic compound film, recombining efficiency of thecarrier has drastically been enhanced by adopting a singleheterostructure such that a hole transporting layer comprising anaromatic diamine compound and an electron transporting light emittinglayer comprising a tris(8-quinolinolato)-aluminum complex (hereinafter,referred to also as “Alq3”) are laminated. The reason can be describedbelow.

For example, in a case of the organic light emitting element having asingle layer of Alq3, since the Alq3 has an electron transportingproperty, most of the electrons injected from the cathode reach theanode without being recombined with holes and the light emittingefficiency is extremely low. Namely, in order to allow the organic lightemitting element having a single layer to effectively emit light (ordrive it at low voltage), it is necessary to use a material which cantransport both electrons and holes (hereinafter, referred to also as“bipolar material”) while the Alq3 does not satisfy such conditions asdescribed above.

However, when the single heterostructure as described in Non-PatentDocument 1 is applied, the electron injected from the cathode is blockedat an interface between the hole transporting layer and the electrontransporting layer, and then, confined in the electron transportinglight emitting layer. Therefore, recombination of the carrier isefficiently performed in the electron transporting light emitting layerto attain an efficient light emission.

Further, it can be said that the organic light emitting element inNon-Patent Document 1 is characterized by a separation of functions suchthat transportation of the hole is performed in the hole transportinglayer, and transportation and light emission of the electron isperformed in the electron transporting layer. Such function separationconcept has further been developed, and then, a technique in which threetypes of functions of the hole transportation, electron transportationand light emission are borne by different materials, respectively, hasbeen proposed. By this technique, a material which has an inferiorcarrier transportation property but has a high light emission efficiencycan be used as a light emitting material and, by adopting this material,the light emission efficiency of the organic light emitting element isenhanced.

A representative technique thereof is doping of a dye (for example,refer to Non-Patent Document 2). Namely, as shown in FIG. 3( a), in asingle-hetero structure comprising the hole transporting layer 101 andthe electron transporting layer 102 (also functioning as a lightemitting layer), a light emission color of the dye 103 within a boundaryregion which is a light emitting region can be obtained by doping thedye 103 in the electron transporting layer 102. A case in which the dye103 is doped in the hole transporting layer 101 side can also beconsidered.

(Non-Patent Document 2): C. W. Tang et al., Journal of Applied Physics,1989, Vol. 65, No. 9, pp 3610-3616.

As compared to this, as shown in FIG. 3( b), there is a technique of adouble heterostructure (three layer structure) in which the lightemitting layer is interposed between the hole transporting layer and theelectron transporting layer (for example, refer to Non-Patent Document3). In a case of this technique, since the hole is injected from thehole transporting layer 106 to the light emitting layer 105 and theelectron is injected from the electron transporting layer 107 to thelight emitting layer 105, respectively, the recombination of the carrieroccurs in the light emitting layer 105, and, accordingly, light emissionhaving a light emission color of the material used as the light emittinglayer 105 is attained.

(Non-Patent Document 3): Chihaya Adachi and three others, JapaneseJournal of Applied Physics, 1988, Vol. 27, No. 2, L269-L271.

An advantage of such function separation as described above lies in apoint that, by performing the function separation, it is not necessaryto simultaneously impart one type of organic material with variousfunctions (a light emission property, a carrier transportation property,a carrier injection property from an electrode, and the like) and,accordingly, a wide range of degree of freedom can be given to amolecular design or the like. (For example, it becomes not necessary tolaboriously explore a bipolar material). Namely, a high light emissionefficiency can easily be attained by combining materials each having anexcellent light emission characteristics, materials each having anexcellent carrier transportation property and the like in various ways.

From the aforementioned advantages, a concept of lamination structureitself (blocking function or function separation of the carrier) asdescribed in Non-Patent Documents 1 to 3 is widely utilized.

In the organic light emitting element subjected to such functionseparation as described above, a technique of doping a coloring materialis particularly effective in extension of a lifetime (for example, referto Patent Document 1). As for factors thereof, mentioned are a smoothenergy transfer to a host material or improvement of a film quality ofthe host material and the like. In Patent Document 1, rubrene is dopedin the hole transporting layer, to thereby extending the lifetime of theelement.

(Patent Document 1): JP-A No. 10-255985.

In Patent Document 1, since a coloring material is also doped into ahole transporting layer, a light emitting element has a structure asshown in FIG. 2 in which the coloring material is doped in each of anelectron transporting layer and the hole transporting layer.

As described above, also in the element as shown in FIG. 2, a lightemitting region is present in a boundary region 203 between the holetransporting layer 201 and the electron transporting layer 202.Therefore, both of two coloring materials of a first doping material anda second doping material which are present in the boundary region 203cause light to be emitted.

In such manner as described above, when light emission occurs at awavelength different from that at which light is intended to be emitted,a light emission color having a high purity can not be obtained. It isnot favorable to use the element which emits light at such differentwavelength in a full-color organic light emitting device which requireslight having a high color purity in each of red, green and blue colors,respectively.

A problem of the present invention is to provide a light emittingelement which can obtain light emission having a high color purity, and,at the same time, consistently emits light at the time of continuousdriving, has a high resistance, has a long lifetime and is high inreliability.

SUMMARY OF THE INVENTION

A light emitting element according to the present invention, in which anorganic compound film comprising a hole transporting material, anelectron transporting material, a first impurity (first dopingmaterial), and a second impurity (second doping material) is providedbetween an anode and a cathode, is characterized in that the organiccompound film is laminated with a first mixed region comprising the holetransporting material and the first impurity, a hole transporting regioncomprising the hole transporting material, a second mixed regioncomprising the electron transporting material and the second impurity,and an electron transporting region comprising the electron transportingmaterial in the stated order from the side of the anode.

The hole transporting region means a region which does not contain anyone of the doping materials and substantially comprises only the holetransporting material. Therefore, by providing the hole transportingregion, it becomes possible to block an electron from being injectedinto the frist mixed region and, accordingly, recombination of theelectron and the hole does not occur in the first mixed regioncomprising the first doping material. Since the recombination does notoccur in the first mixed region, the first doping material does notexhibit light emission. As a result, according to the present invention,only the second doping material can emit light, and then, by using alight emitting material that is to perform light emission as the seconddoping material, a light emitting element which can obtain only desiredlight emission can be manufactured. Further, according to the presentinvention, a long lifetime of the organic light emitting elementcompared with the organic light emitting element in which the firstdoping material is not doped in the hole transporting material isrealized and a consistent light emission can be obtained at the time ofcontinuous driving.

Therefore, according to the present invention, the light emittingelement which can obtain light emission having a high color purity and,at the same time, consistently emits light at the time of continuousdriving, has a high resistance, has a long lifetime and is high inreliability can be obtained.

Further, a method for manufacturing a light emitting element accordingto the present invention, in which an organic compound film comprising ahole transporting material, an electron transporting material, a firstimpurity and a second impurity is provided between an anode and acathode, is characterized by comprising, in the organic compound film,the steps of: forming a first mixed region comprising the holetransporting material and the first impurity adjacent to the anode;forming a hole transporting region comprising the hole transportingmaterial adjacent to the first mixed region; forming a second mixedregion comprising the electron transporting material and the secondimpurity adjacent to the hole transporting region; and forming anelectron transporting region comprising the electron transportingmaterial adjacent to the second mixed region.

In such structure as described above, the first impurity (first dopingmaterial) or the second impurity (second doping material) may be acoloring material.

Further, in the aforementioned structure, by providing the holetransporting region, the electron is blocked from being injected intothe first mixed region, to thereby allow only the second doping materialto emit light. However, when thickness of the hole transporting regionis unduly small, the electron is not sufficiently blocked, passestherethrough, and then, injected to the first mixed region and, as aresult, the first doping material also emits light. For this account, itis preferable that a ratio of a film thickness of the hole transportingregion to a total film thickness of the mixed region and the holetransporting region is 10% or more.

Further, by doping the first impurity (first doping material) by a fewpercentages by weight in the hole transporting material, there is aneffect of extending a lifetime compared with an element in which dopingis not performed. As for the first doping material, a polycycliccompound such as rubrene is appropriate and a concentration thereof ispreferably in the range of from 0.1% by weight to 10% by weight.

Therefore, an electric apparatus using a light emitting devicecomprising such light emitting element according to the presentinvention as has been described as a display portion or the like hashigh visibility and reliability and, accordingly, is extremely useful.

Further, the light emitting device as used herein means an image displaydevice which uses the organic light emitting element as a light emittingelement. Further, a module in which a connector, for example, anAnisotropic Conductive Film (ACF), a TAB (Tape Automated Bonding) tapeor a TCP (Tape Carrier Packege) is attached to the organic lightemitting element, another module in which a printed circuit board isprovided at a tip of the TAB tape or the TCP, and still another modulein which IC (integrated circuit) is directly mounted on the organiclight emitting element by a COG (Chip on Glass) method are all includedin the light emitting device.

According to the present invention, a light emitting element which canobtain light emission having a high color purity and, at the same time,consistently emits light at the time of continuous driving, has a highresistance, has a long lifetime and is high in reliability can beobtained. Therefore, an electric apparatus using a light emitting devicecomprising a light emitting element according to the present inventionas a display portion or the like has also high visibility andreliability and, accordingly, is extremely useful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure of an organic light emitting element according tothe present invention;

FIG. 2 is an example of a structure of an organic light emitting elementin which two types of conventional dyes are doped;

FIGS. 3( a)-3(b) are examples of structures of an organic light emittingelement in which one type of a conventional dye is doped;

FIG. 4 is a diagram of an vapor deposition device to be used formanufacturing an element in Example 1;

FIG. 5 shows EL spectra in light emitting elements for the purpose ofcomparing the light emitting element according to the present inventionwith a conventional one;

FIG. 6 is a graph showing a relation between a constant current drivingtime and a normalization brightness of a light emitting element for thepurpose of comparing the light emitting element according to the presentinvention with a conventional one;

FIGS. 7( a)-7(b) is a top view and a cross-sectional view in Example 2;

FIGS. 8(A)-8(C) is a diagram showing examples of electronic apparatuses(Example 3); and

FIGS. 9( a)-9(e) is a diagram showing examples of electronic apparatuses(Example 3).

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Hereinafter, embodiments according to the present invention will bedescribed with reference to FIG. 1.

FIG. 1 is an example of a light emitting element according to thepresent invention. An organic compound film (electrically conductivelayer) interposed between an anode 301 and a cathode 302 has a structurecomprising, in a direction of from the anode 301 to the cathode 302, afirst mixed region 303 comprising both a hole transporting material anda frist doping material, a hole transporting region 304 comprising onlythe hole transporting material, a second mixed region 305 comprisingboth electron transporting material and a second doping material, and anelectron transporting region 306 comprising only the electrontransporting material. By the structure as shown in FIG. 1, lightemission is performed only at a desired wavelength and a consistentlight emission can be obtained during continuous driving.

Further, in the organic light emitting element, in order to take outlight emission, at least one of a first electrode and a second electrodemay be transparent. As for such transparent electrode, ITO isrepresentatively used. Still further, a material in which SiO₂ of from0.1 to 10% by weight is added to ITO or another material in which ZnO offrom 0.1 to 10% by weight is added to ITO may be used. The article inwhich SiO₂ of from 0.1 to 10% by weight is added to ITO can improveflatness of a surface of ITO and prevent a short-circuit between top andbottom electrodes. Although an element structure in which the firsttransparent electrode (anode) is formed on a substrate and light istaken out from the first electrode is ordinarily used, structures inwhich a cathode is formed as the first electrode and light is taken fromthe cathode and in which light is taken out from a reverse side oppositeto the substrate are also applicable.

Light emission of the organic light emitting element to be applicable tothe present invention may exhibit any light emission color. When afull-color light emission device or the like is manufactured, aplurality of light emitting elements which emit light at differentcenter wavelengths, respectively, may be combined. Such method asdescribed above is appropriate for being applied by the presentinvention. Further, a method in which a color filter is combined withthe organic light emitting element which exhibits a white light emissioncolor, another method in which a color conversion layer is combined withthe organic light emitting element which exhibits a blue light emissioncolor or the like may be used. Particularly, the present invention ispreferably applied to a method in which three primary colors (blue, redand green) are combined together.

Further, a structure in which a hole injection layer comprising a holeinjecting material is formed between the anode and the first mixedregion, or an electron injection layer comprising an electron injectingmaterial is formed between the cathode and the second mixed region ispermissible.

Next, favorable materials for the hole injecting material, the holetransporting material, the electron transporting material, the electroninjecting material, the light emitting material and the like aredescribed below. However, the materials for use in the light emittingelement according to the present invention are not limited thereto.

As for the hole injecting material, when it is an organic compound, aporphyrin-type compound is effective. Examples of such compounds includephthalocyanine and copper phthalocyanine (hereinafter, referred to alsoas “CuPc”). When it is a polymeric compound, polyvinyl carbazole and thelike can be mentioned. However, as described previously, there is amaterial in which a chemical doping is performed on a conjugatedelectrically conductive polymeric compound and, on this connection,polyethylene dioxythiophene in which polystyrene sulfonic acid is doped,polyaniline in which a Lewis acid of iodine or the like is doped,polypyrrole or the like is mentioned. Further, an insulator of polymericcompound is so effective on a point of flattening the anode thatpolyimide is mentioned. Still further, an inorganic compound is alsoused and, on this connection, not only a thin metallic film of, forexample, gold or platinum but also an ultra-thin film of aluminum oxideor the like is mentioned.

A material that is most widely used as the hole transporting material isan aromatic amine-type (namely, having a benzene-nitrogen bond)compound. Examples of such materials as widely used include4,4′-bis-(diphenylamino)-biphenyl; derivatives thereof such as4,4′-bis-[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl and4,4′-bis-[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (hereinafter, referredalso as “α-NPD” for short); and star burst aromatic amine compounds suchas 4,4′,4″-tris (N,N-diphenyl-amino)-triphenyl amine and 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenyl amine.

As for the electron transporting material, a metal complex is oftenused. Examples of such electron transporting materials include metalcomplexes each having a quinoline skeleton or a benzoquinoline skeleton,such as Alq3 as previously described,tris(4-methyl-8-quinolinolato)aluminum (hereinafter referred to also as“Almq”), and bis(10-hydroxybenzo[h]-quinolinato)beryllium (hereinafterreferred to also as “Bebq”); and mixed ligand complexes such asbis(2-methyl-8-quinolinolato)-(4-hydroxy-biphenylyl)-aluminum(hereinafter referred to also as “BAlq3”). Examples of these materialsalso include metal complexes each having an oxazole-based orthiazole-based ligand such as bis[2-(2-hydroxypheyl)-benzoxazolato]zinc(hereinafter referred to also as “Zn(BOX)₂”) andbis[2-(2-hydroxypheyl)-benzothiazolato]zinc (hereinafter referred toalso as “Zn(BZT)₂”). Other than these metal complexes, oxadiazolederivatives such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole and1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene; triazolederivatives such as3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)1,2,4-triazole and3-(4-tert-butylphenyl)-4-(4-ethylpheyl)-5-(4-biphenylyl)-1,2,4-triazole;and phenanthroline derivatives such as bathophenanthroline andbathocuproine each have an electron transporting property.

As for the electron injecting material, any one of the aforementionedelectron transporting materials can be used. Other than these materials,an insulating ultra-thin film of alkaline metal halides such as lithiumfluoride and alkaline metal oxides such as lithium oxide are often used.Further, alkaline metal complexes such as lithium acetylacetonate and8-quinolinolato-lithium are also effective.

As for the light emitting material, not only metal complexes such asAlq3, Almq, BeBq, BAlq, ZN(BOX)₂, and ZN(BTZ)₂, but also various typesof fluorescent dye to be used as the second doping material areeffective. As for fluorescent dyes, quinacridone derivatives such asgreen-colored quinacridon, 2,9-dimethylquinacridon,benzo-[h]-benzo-[7,8]-quino-[2,3-b]-acridine-7,16-dimethyl-9,18-dihydro(hereinafter referred to also as “DMNQA”), blue-colored perylene,reddish orange-colored4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran arementioned. Further, triplet light-emitting materials are also possibleand a complex having platinum or iridium as a center metal is usedmainly. As for the triplet light-emitting materials,tris(2-phenylpyridine)iridium, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin-platinum and the like are mentioned.

As for the first doping material that is doped in the hole transportinglayer, a polycyclic compound such as rubrene-type is used. Particularly,rubrene is used as a favorable material. Further, TBT (tert-butylperylene) or DDPA (9,10-di(3,5-diphenyl) anthrathene can be used.

Materials having respective functions as described above are combined invarious ways, and then, by applying any one of the resultant combinationto the light emitting element according to the present invention, anorganic light emitting element which can obtain light emission at adesired wavelength and has a long lifetime can be manufactured.

The present invention having the aforementioned structure will beexplained in more detail in embodiments to be described below.

EMBODIMENTS Example 1

In the present embodiment, a method for manufacturing, by using a vapordeposition device as shown in FIG. 4, an organic compound film and asecond electrode (cathode) on a substrate on which a transparentelectrode such as ITO has previously been prepared is shown.

The vapor deposition device as shown in FIG. 4 comprises a transportchamber 401 (attached with a transport robot 402 for use in transportinga substrate, a counter substrate or metal mask), a substrate/mask stockchamber 403 connected to the transport chamber 401, a pretreatmentchamber 404, a first organic vapor deposition chamber 405, a secondorganic vapor deposition chamber 406, a metal vapor deposition chamber407, a CVD chamber 408, a sealing glass stock chamber 409 and a sealingchamber 410.

Firstly, loading of a substrate and a metal mask for vapor deposition isperformed in the substrate/mask stock chamber. The substrate/mask stockchamber is constituted such that it has an elevator structure (in thepresent embodiment, having 11 steps) and allows each step to beserviceable for both the substrate (in the present embodiment, being setas 126.6 mm×126.6 mm) and the mask. It has a maximum loading capacity often pieces of the substrate and the mask in total. Since remaining onestep functions as a substrate heating step for heating the substrate, itis allowed to be empty when the substrate or the mask is loaded.Further, in the manufacturing device in the present embodiment, adirection of the substrate is set to be facedown at all times.

Next, loading of a counter substrate is performed in a sealing glassstock chamber. The sealing glass stock chamber is constituted such thatit has an elevator structure (in the present embodiment, having tensteps) and allows each step to have a maximum loading capacity of tenpieces of pretreated (representatively, denoting being subjected totreatments of attaching a desiccant for absorbing moisture inside andoutside of a panel and applying a sealant for bonding with thesubstrate) counter substrates (in the present embodiment, being set as126.6 mm×126.6 mm each). Further, in the manufacturing device accordingto the present invention, a direction of the counter substrate is set tobe face up at all times.

In the manufacturing device according to the present invention, afilm-forming treatment is completed prior to other treatments on all ofloaded substrates. This is called as a “vapor deposition mode”. Afterthe vapor deposition mode is completed, the procedure proceeds to a“sealing mode” in which bonding of the counter substrate is performed.

Hereinafter, taking, for example, the case where seven substrates andthree masks are used, the vapor deposition mode is described.

Firstly, the transport chamber is evacuated to be in a high vacuum.During the vapor deposition, the transport chamber is maintained to bein a high vacuum. Next, after the substrate/mask stock chamber isevacuated, the masks are transported into the first organic vapordeposition chamber, the second organic vapor deposition chamber, and themetal vapor deposition chamber, respectively. In the presentmanufacturing device, there are three film-forming chambers which eachuse the mask. After preparations as described above are completed, thesubstrate is transported into the pretreatment chamber. In thepretreatment chamber, heating of the substrate in a vacuum and a plasmatreatment by using a single gas system (for example, 02 plasmatreatment) are both possible and such treatments as described above areperformed on an entire surface of the substrate.

Further, since it is possible to perform the heating of the substrate ona substrate heating step in the mask stock chamber, the heating of thesubstrate may be performed there in order to aim at a throughputimprovement. In the present embodiment, vacuum heating of the substrateis performed in the substrate/mask stock chamber after evacuated.Namely, the substrate is transported from the substrate/mask stockchamber onto the substrate heating step in the substrate/mask stockchamber via the transport chamber, and then, heating is performed by aheater. After the heating is completed, the substrate is transportedinto the pretreatment chamber via the transport chamber, and then,cooled (namely, left to stand in the pretreatment chamber). By sucharrangement as described above, even in period in which the substrate isbeing cooled, it becomes possible to heat a next substrate in a vacuumin the substrate/mask stock chamber, to thereby improve the throughput.

Next, the substrate is transported from the pretreatment chamber to thesecond organic vapor deposition chamber via the transport chamber, andthen, after the substrate is subjected to an alignment with a mask byusing two CCD cameras, 20 nm of a hole injecting layer CuPc is formedthereon. In the second organic vapor deposition chamber, a material isallowed to be evaporated from fixed vapor deposition sources (in thepresent embodiment, being set as eight sources), and then, a filmthereof is formed on a substrate located over. The substrate is rotatedwhile the vapor deposition is performed. By such rotation, a thicknessdistribution within a surface of the film on the substrate is improved.After the CuPc is formed, the hole transporting layer is formed.Firstly, 20 nm of a mixed region in which 5% by weight of rubrene isdoped in an α-NPD is formed by a co-vapor deposition method. After themixed region of the α-NPD and the rubrene is formed, 20 nm of non-dopedlayer that is constituted only by the α-NPD is continuously formed onlyby closing the vapor deposition source attached to the rubrene vapordeposition source.

Next, the substrate is transported to the first organic vapor depositionchamber via the transport chamber. A mechanism and a film-formingtreatment method are completely same as those in the second organicvapor deposition chamber except that there are six vapor depositionsources. Here, Alq3 which simultaneously acts as the light emittinglayer and the electron transporting layer is formed. Particularly, aminute amount (for example, about 0.5% by weight) of DMNQA is doped inthe light emitting layer by the co-vapor deposition method. By suchdoping, a panel lifetime of a completed panel is substantially improved.Further, shifting from the light emitting layer to the electrontransporting layer is smoothly conducted only by closing a vapordeposition source shutter attached to a DMNQA vapor deposition source.By such method as described above, 37.5 nm of the light emitting layerand 37.5 nm of the electron transporting layer are formed.

Next, the substrate is transported into the metal vapor depositionchamber via the transport chamber. In this chamber, 1 nm of the electroninjecting layer CaF2 and 200 nm of the cathode A1 are formed. In themetal vapor deposition chamber, film-forming can be performed by using aresistive heating method (12 positions of resistive heating vapordeposition sources in total (six-position system×2) exist), an EB method(six positions of EB vapor deposition sources in total (six-positionsystem ×1) exist); however, when a damage to the TFT on the substrate istaken into consideration, it is desirable to use the resistive heatingmethod. A mechanism and a film-forming treatment method are completelysame as those in the first and second organic vapor deposition chambersexcept for vapor deposition sources.

Further, in the CVD chamber, it is possible to form a CVD film on anentire surface of the substrate. Still further, it is also possible toperform a plasma treatment by using plural types of gases. By making useof this, for example, a silicon nitride film may be formed on a cathodeA1 as a protective film or a plasma treatment by using plural types ofgases (for example, Ar+O₂ plasma treatment) may be performed on thesubstrate.

The substrate that has been subjected to necessary treatments asdescribed above is back to the substrate/mask stock chamber at astarting point via the transport chamber. Further, a series oftreatments necessary for obtaining a single-colored panel ofgreen-colored light emission has been described; however, the presentinvention is not limited thereto.

When same treatments as described above are completed on all of theloaded substrates and recovered from each vapor deposition chamber tothe substrate/mask stock chamber, the vapor deposition is completed, andthen, the present manufacturing device subsequently enters into thesealing mode.

Further, in the aforementioned description, raised is a case in whichthree masks to be used are set in the vapor deposition chamber inadvance and they are not changed during the vapor deposition treatment,namely, a case of “no mask change mode”. However, depending on anelement structure, it goes without saying that a request for using aplurality of masks every vapor deposition chamber appears. Even in suchcase, the present manufacturing device can correspond to this requestand three or more masks are set in the substrate/mask stock chamber inadvance, and then, masks may be changed in an interval betweentreatments in the vapor deposition chamber (however, as the number ofthe masks to be used is increased, the number of the substrates to betreated at the same time is of course decreased. This is called as“mask-change mode” and is separated from the aforementioned mode.

The sealing mode is now described below.

Firstly, it is necessary to allow the transport chamber, thesubstrate/mask stock chamber, the sealing glass stock chamber back to bein a normal pressure. As for the transport chamber and thesubstrate/mask stock chamber, immediately after the vapor depositionmode is completed, a vent treatment may be performed. The vent treatmentdenotes a treatment of injecting a gas into a chamber which has beenevacuated to be in a low pressure and recovering the chamber to be in anormal pressure. In the present embodiment, nitrogen is used as a gas tobe injected for the paint treatment. As for the sealed glass stockchamber, by setting the counter substrate which has been subjected tothe pretreatment immediately before the sealing as far as possible,deterioration of a sealant or desiccant can be prevented. After thecounter substrate is set, by performing evaluation and the venttreatment on the sealing glass stock chamber several times (in thepresent embodiment, being set as two times), not only reduction ofmoisture content in the transport chamber at the time of the sealingmode can be prevented, but also defoaming of the sealant applied on thecounter substrate can be performed. It is ideal that, immediately afterthe last vent treatment in the sealing glass stock chamber is completed,the sealing treatment is started. This can be realized by properlysetting, by an operator, a timing of each of the vent treatment in thetransport chamber and the substrate/mask stock chamber, the loading ofthe counter substrate in to the sealing glass stock chamber, and thevent treatment in the sealing glass stock chamber.

Next, the substrate is transported from the substrate/mask stock chamberto the sealing chamber via the transport chamber, while the countersubstrate is transported from the sealing glass stock chamber to thesealing chamber via the transport chamber. In the sealing chamber, afteran alignment (position alignment) between the substrate and the countersubstrate is completed such that positions of both peripheral end facesare aligned each other, the substrate and the counter substrate arebonded with each other, and sealed by putting pressure. Further, a UVirradiation is performed from the side of the counter substrate (lowerside), to thereby cure the sealant (in the present embodiment, being setas a UV-curable resin). On this occasion, it is possible to use ashielding mask and to selectively perform the UV irradiation only on asealant portion. Still further, in the present embodiment, the shieldingmask is an article in which a Cr film is formed on quartz glass and,since it is impossible to transport it into the transport chamber by atransport robot, the operator directly sets it in the sealing chamber.

By performing such sealing treatment as described above, the substrateand the counter substrate are combined with each other to be a panel ina unit. The resultant panel is transported from the sealing chamber tothe substrate/mask stock chamber via the transport chamber.Subsequently, next substrate and counter substrate are subjected to sametreatments as those described above. In the end, seven panels arestocked in the substrate/mask stock chamber and the sealing mode isterminated.

After the sealing mode is completed, the panel may be taken out of thesubstrate/mask stock chamber.

A series of treatments in the vapor deposition mode and the sealing modecan automatically be performed by using a control system. Wheninformation including a transport route, treatment details and the likeevery substrate are registered, by only sending a signal of starting thetreatment, a series of treatments are automatically performed on eachsubstrate in accordance with the registered information.

COMPARATIVE EXAMPLE 1

A light emitting element was manufactured in a same manner as in Example1 except that, in forming a hole transporting layer, 40 nm of a layer inwhich 5% by weight of rubrene was doped in an α-NPD was formed by aco-vapor deposition method without forming a non-doped layer.

In regard to the elements manufactured in Example 1 and ComparativeExample 1, EL spectra at the time of 125 mA/m² of current density areshown in FIG. 5. As for the EL spectra, light emission from the side ofthe substrate was measured on each element. In the light emittingelement manufactured by a method in Example 1, spectrum 501 caused byDMNQA which was doped in an electron transporting layer was observed.However, in the light emitting element manufactured by a method inComparative Example 1, not only light emission of DMNQA but alsospectrum 503 which contains a peak caused by rubrene doped in the holetransporting layer was observed.

In such a manner as described above, the light emitting elementmanufactured in Comparative Example 1 exhibits light emission of twotypes of materials, while that manufactured in Example 1 exhibits lightemission of one type of material. Therefore, in order to obtain a lightemission color having a high purity only at a desired wavelength, it wasconfirmed that it is desirable to use the element manufactured inExample 1.

COMPARATIVE EXAMPLE 2

A light emitting element was manufactured in a same manner as in Example1 except that, in forming a hole transporting layer, 40 nm of only α-NPDwas formed without forming a mixed region.

In regard to the elements manufactured in Example 1 and ComparativeExample 2, EL spectra at the time of 125 mA/m² of current density areshown in FIG. 5. As for the EL spectra, light emission from the side ofthe substrate was measured on each element. In the light emittingelements manufactured by a method in Example 1 and a method inComparative Example 2, spectra 501 and 502 caused by DMNQA which wasdoped in an electron transporting layer were observed.

Further, in regard to light emitting elements manufactured in Example 1and in Comparative Example 2, brightness deterioration against theelapsed time at the time the elements were subjected to a constantcurrent driving with a current value which allows an initial brightnessto be 1000 cd/m² is shown in FIG. 6.

When a time-brightness curve 601 of the light emitting elementmanufactured in Example 1 and a time-brightness curve 602 of the lightemitting element manufactured in Comparative Example 2 were comparedwith each other, the light emitting element manufactured in Example 1showed a slow brightness deterioration against the elapsed time comparedwith the other one.

Therefore, it was confirmed that the light emitting element manufacturedin Example 1 according to the present invention can obtain a lightemission color having a high purity and can be a light emitting elementhaving a long lifetime.

Example 2

In the present embodiment, a light emitting device having an electricfield light emitting element according to the present invention in apixel portion is described with reference to FIG. 7. Further, FIG. 7( a)is a top plan view showing a light emitting device, while FIG. 7( b) isa cross-sectional view taken along the line B-B′ of FIG. 7( a). As shownby dotted lines, 701 denotes a driver circuit (source side drivercircuit) portion; 702 denotes a pixel portion; and 703 denotes a drivercircuit (gate side driver circuit) portion. Further, 704 denotes asealing substrate; 705 denotes a sealant; and an inside 707 surroundedby the sealant 705 is a space.

Further, 708 denotes a wiring for transmitting signals to be inputted inthe source side driver circuit portion 701 and the gate side drivercircuit portion 703 and receives signals such as a video signal, a clocksignal, a start signal and a reset signal from an FPC 709 which becomesa an outer input terminal. Furthermore, on this occasion, although onlythe FPC is shown, a printed wiring board (hereinafter, referred to alsoas “PWB”) may be attached thereto. In the light emitting device asdescribed herein, not only a main body of the light emitting device, butalso that attached with the FPC or the PWB is included.

Next, a cross-sectional structure thereof is described with reference toFIG. 7( b). On an element substrate 710, the driver circuit portion andthe pixel portion are formed. On this occasion, the source side drivercircuit 701 which is the driver circuit portion and the pixel portion702 are shown.

Further, in the source side driver circuit 701, a CMOS circuit in whichan n channel-type TFT 723 and a p channel-type TFT 724 are combined witheach other is formed. Still further, the TFT which forms the drivercircuit may be formed by a known CMOS circuit, a PMOS circuit, or anNMOS circuit. Furthermore, in the embodiments according to the presentinvention, although a driver integrated type in which the driver circuitis formed on the substrate is shown, such structure is not alwaysrequired and the driver circuit may not be formed on the substrate andmay be formed outside the substrate.

Further, the pixel portion 702 is formed by a plurality of pixelscontaining a switching TFT 711, a current control TFT 712 and a firstelectrode 713 electrically connected to a drain thereof. Still further,an insulator 714 is formed such that it covers an end portion of thefirst electrode 713 and, on this occasion, it is formed by using apositive-type photosensitive acrylic resin film.

Further, in order to secure coverage, a curved face having a curvatureis allowed to be formed in a top end portion or a bottom end portion ofthe insulator 714. For example, when the positive-type photosensitiveacrylic resin is used as a material of the insulator 714, it ispreferable to form a curved face having a curvature radius (0.2 μm to 3μm) only on the top end portion of the insulator 714. Still further, asfor the insulator 714, any one of a negative type one which becomesinsoluble to an etchant by photosensitive light and a positive type onewhich becomes soluble to the etchant by photosensitive light can beused.

On the first electrode 713, an organic compound layer 716 and a secondelectrode 717 are each formed. On this occasion, as for a material ofthe first electrode 713 which functions as an anode, it is desirablethat a material having a large work function is used. For example, asingle layer film such as an ITO film, an indium zinc oxide film, atitanium nitride film, a chromium film, a tungsten film, a Zn film, a Ptfilm; a laminated layer of titanium nitride and a film comprising,aluminum as a main component; a three-layer structure of a titaniumnitride film, a film comprising, as a main component, aluminum and atitanium nitride; or the like can be used. Further, when it takes alaminate structure, it is low in resistance as wiring, it can obtain afavorable ohmic contact and, moreover, it can function as an anode.

Further, the organic compound layer 716 uses the structure in any one ofembodiments or in Example 1 according to the present invention. Fordetails, the embodiments and Example 1 may be referred.

Further, as for the material to be used in the second electrode(cathode) 717 to be formed on the organic compound layer 716, a materialhaving a small work function (Al, Ag, Li, Ca, or alloys thereof such asMgAg, MgIn, AlLi, CaF₂ or CaN) may be used. Still further, when lightgenerated in the electric field light emission layer 716 is allowed topass through the second electrode 717, as for the second electrode(cathode) 717, a laminated layer of a metallic thin film with a reducedfilm thickness and a transparent electrically conductive film (ITO, analloy of indium oxide and zinc oxide, zinc oxide or the like) may beused.

Further, by bonding the sealing substrate 704 with the element substrate710 by the sealant 705, a structure in which an organic light emittingelement 718 is provided in the space 707 which is surrounded by theelement substrate 701, the sealing substrate 704 and the sealant 705 isconstructed. Still further, another structure in which an inert gas(nitrogen, argon or the like) is filled, or the sealant 705 is filled inthe space 707 is also included.

Further, it is preferable that an epoxy resin is used as the sealant705. Still further, such materials as described above do not allowmoisture or oxygen to permeate them as much as possible are desirable.Furthermore, as for the material to be used in the sealing substrate704, not only a glass substrate and a quartz substrate, but also aplastic substrate comprising a polyimide, a polyamide, an acrylic resin,an epoxy resin, PES, PC, PET, PEN or the like can be used.

In such a manner as described above, the light emission device havingthe organic light emitting element according to the present inventioncan be obtained.

Example 3

The light emitting device according to the present invention as has beendescribed above has advantages in that a light emission color is high inpurity and it has a long lifetime. Therefore, electric apparatuses eachhaving the aforementioned light emitting device as a display portion arehigh in visibility and reliability and, accordingly, are extremelyuseful.

By using the light emitting device comprising the light emitting elementmanufactured in accordance with the present invention, various types ofmodules (active matrix type liquid crystal module, active matrix type ELmodule and active matrix type EC module) can be manufactured and,moreover, electronic apparatuses in which any one of these modules ismounted can be manufactured.

Examples of such electronic apparatuses include a video camera, adigital camera, a head mount display (goggle-type display), a carnavigation system, a projector, a car stereo, a personal computer and aportable information terminal (such as mobile computer, cellulartelephone or electronic book). Examples of these appliances are shown inFIGS. 8 and 9.

FIG. 8(A) shows the cellular telephone comprising a main body 801, asound output portion 802, a sound input portion 803, a display portion804, an operation switch 805, an antenna 806, an image input portion(CCD, image sensor or the like) 807 and the like. By manufacturing thecellular telephone in which the light emitting device comprising thelight emitting element according to the present invention is used in thedisplay portion 804, the cellular telephone having a high visibility anda high reliability can be realized.

FIG. 8(B) shows a portable book (electronic book) comprising a main body808, display portions 809 and 810, a memory medium 811, an operationswitch 812, an antenna 813 and the like. By manufacturing the portablebook (electronic book) in which the light emitting device comprising thelight emitting element according to the present invention is used in thedisplay portion 809, the portable book (electronic book) having a highvisibility and a high reliability can be realized.

FIG. 8(C) shows a display comprising a main body 814, a support base815, a display portion 816 and the like. By manufacturing the display inwhich the light emitting device comprising the light emitting elementaccording to the present invention is used in the display portion 816,the display having a high visibility and a high reliability can berealized.

Note that, the display shown in FIG. 8(C) is that of a small- tomedium-sized type or a large-sized type, for example, having a screensize of 5 to 20 inches. Moreover, it is preferable to perform amass-production by executing a multiple pattern using a substrate havinga side of 1 m to form the display portion of such size as describedabove.

FIG. 9(A) shows a personal computer comprising a main body 901, an imageinput portion 902, a display portion 903, a keyboard 904 and the like.By manufacturing the personal computer in which the light emittingdevice comprising the light emitting element according to the presentinvention is used in the display portion 903, the personal computerhaving a high visibility and a high reliability can be realized.

FIG. 9(B) shows a video camera comprising a main body 905, a displayportion 906, a sound input portion 907, an operation switch 908, abattery 909, an image receiving portion 910 and the like. Bymanufacturing the video camera in which the light emitting devicecomprising the light emitting element according to the present inventionis used in the display portion 906, the video camera having a highvisibility and a high reliability can be realized.

FIG. 9(C) shows a mobile computer comprising a main body 911, a cameraportion 912, an image receiving portion 913, an operation switch 914, adisplay portion 915 and the like. By manufacturing the mobile computerin which the light emitting device comprising the light emitting elementaccording to the present invention is used in the display portion 915,the mobile computer having a high visibility and a high reliability canbe realized.

FIG. 9(D) shows a player using a record medium recorded with a program(hereinafter, referred to also as record medium) comprising a main body916, a display portion 917, a speaker portion 918, a record medium 919,an operation switch 920 and the like. Moreover, the player uses DVD(Digital Versatile Disc), CD and the like as the record medium and canenjoy music, enjoy movie, play a game, and be on the Internet. Bymanufacturing the player in which the light emitting device comprisingthe light emitting element according to the present invention is used inthe display portion 917, the player having a high visibility and a highreliability can be realized.

FIG. 9(E) shows a digital camera comprising a main body 921, a displayportion 922, an eye piece portion 923, an operation switch 924, an imagereceiving portion (not shown) and the like. By manufacturing the digitalcamera in which the light emitting device comprising the light emittingelement according to the present invention is used in the displayportion 922, the digital camera having a high visibility and a highreliability can be realized.

As has been described above, the range of applications of the presentinvention is extremely wide and the present invention is applicable tomanufacturing methods of electronic apparatuses in various fields.Further, the electronic apparatuses described in the present embodimentaccording to the present invention can be realized by structures of anycombinations of embodiments and Examples 1 and 2.

1. A method for manufacturing a light emitting element in which anorganic compound film comprising a hole transporting material, anelectron transporting material, a first impurity and a second impurityis provided between an anode and a cathode, comprising, in the organiccompound film, the method comprising the steps of: forming a first mixedregion comprising the hole transporting material and the first impurityon the anode; forming a hole transporting region comprising the holetransporting material on the first mixed region; forming a second mixedregion comprising the electron transporting material and the secondimpurity on the hole transporting region; and forming an electrontransporting region comprising the electron transporting material on thesecond mixed region.
 2. A method for manufacturing a light emittingelement according to claim 1, wherein the first impurity and the secondimpurity comprise a coloring material.
 3. A method for manufacturing alight emitting element according to claim 1, wherein a ratio of a filmthickness of the hole transporting region to a total film thickness ofthe first mixed region and the hole transporting region is 10% or more.4. A method for manufacturing a light emitting element according toclaim 1, wherein a concentration of the first impurity in the first mixregion is in the range of from 0.1% by weight to 10% by weight.
 5. Amethod for manufacturing a light emitting element according to claim 1,wherein the light emitting element is mounted in an electronic apparatusselected from the group consisting of a video camera, a digital camera,a head mount display, a car navigation system, a projector, a personalcomputer, and a portable information terminal.
 6. A light emittingdevice having a light emitting element, the light emitting elementcomprising: an anode; a first organic compound layer comprising a holetransporting material and a first impurity on the anode; a secondorganic compound layer essentially consisting of a hole transportingmaterial on the first organic compound layer; a third organic compoundlayer comprising an electron transporting material and a second impurityon the second organic compound layer; a fourth organic compound layeressentially consisting of the electron transporting material on thethird organic compound layer; and a cathode on the fourth organiccompound layer.
 7. A light emitting device, according to claim 6,wherein the first impurity and the second impurity comprise a coloringmaterial.
 8. A light emitting device, according to claim 6, wherein aratio of a film thickness of the hole transporting region to a totalfilm thickness of the first mixed region and the hole transportingregion is 10% or more.
 9. A light emitting device, according to claim 6,wherein a concentration of the first impurity in the first mix region isin the range of from 0.1% by weight to 10% by weight.
 10. A lightemitting device, according to claim 6, wherein the light emittingelement is mounted in an electronic apparatus selected from the groupconsisting of a video camera, a digital camera, a head mount display, acar navigation system, a projector, a personal computer, and a portableinformation terminal.
 11. A method for manufacturing a light emittingdevice comprising the steps of: forming a first organic compound layercomprising a hole transporting material and a first impurity on theanode; forming a second organic compound layer essentially consisting ofa hole transporting material on the first organic compound layer;forming a third organic compound layer comprising an electrontransporting material and a second impurity on the second organiccompound layer; forming a fourth organic compound layer essentiallyconsisting of the electron transporting material on the third organiccompound layer; and forming a cathode on the fourth organic compoundlayer.
 12. A method for manufacturing a light emitting element accordingto claim 11, wherein the first impurity and the second impurity comprisea coloring material.
 13. A method for manufacturing a light emittingelement according to claim 11, wherein a ratio of a film thickness ofthe hole transporting region to a total film thickness of the firstmixed region and the hole transporting region is 10% or more.
 14. Amethod for manufacturing a light emitting element according to claim 11,wherein a concentration of the first impurity in the first mix region isin the range of from 0.1% by weight to 10% by weight.
 15. A method formanufacturing a light emitting element according to claim 11, whereinthe light emitting element is mounted in an electronic apparatusselected from the group consisting of a video camera, a digital camera,a head mount display, a car navigation system, a projector, a personalcomputer, and a portable information terminal.